The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Vehicle systems include powertrain systems that provide output torque for propulsion. Powertrain systems include hybrid systems, all-electric systems, and extended-range electric systems that may be configured to operate in various operating modes to generate and transfer torque to a driveline. Such powertrain systems use torque-generative devices, clutches and transmissions. Torque-generative devices may include internal combustion engines and electrically-powered motor/generators, i.e., electric machines. Known electric machines interact with energy storage devices, e.g., high-voltage batteries. Known high-voltage batteries include those fabricated from lithium-ion cells. Known energy storage device devices configured to store electric energy on-vehicle include high-voltage electrical cells and ultracapacitors, among others.
Known parameters associated with monitoring an energy storage device include a state-of-charge, current, and voltage. Available battery power describes battery power limits that include an allowable range between minimum and maximum allowable battery power levels. Allowable battery power limits are preferably established at threshold levels to prevent either overcharging or overdischarging of an energy storage device. Exceeding allowable battery power limits may result in damage that reduces service life of an energy storage device. It is known that overaggressive limitations in the allowable battery power limits may result in underutilization, with attendant reduction in output torque generated using electric power. In hybrid powertrain systems and extended-range electric systems, there may be a corresponding increase in output torque generated using an internal combustion engine and an associated increase in fuel consumption.
Known hybrid controls systems determine commanded output torque by subjecting an operator torque request to system constraints that include motor torque limits, battery power limits, and clutch torque limits. When an output torque request violates any of the limits, the output torque is modified to protect the hardware. Such operation may not be consistent with minimizing fuel consumption or achieving optimal fuel economy. Known control schemes control the output torque to optimize battery power and/or minimize fuel consumption, with a torque determination control scheme that determines an output torque that consumes optimum battery power. A battery power-based optimum output torque may differ from an operator torque request. When a battery power-based optimum output torque is used as a commanded output torque, drivability may be negatively affected.